Within the fields of medical care and devices, there exists an important unmet medical need for a simple yet effective knee muscle strengthening device. Such strengthening may act to prevent surgery for those who have injured their knee. The universally accepted method for strengthening the knee involves the strengthening of the vastus medialis muscle, whose weakness is responsible for 99% of all chronic knee injuries. See, for example, A. A. Halpern, “The Runner's World Knee Book, What Every Athlete Needs to Know about the Prevention and Treatment of Knee Problems,” New York, Collier Books, 1984. Unfortunately, most people suffering from knee pain do not understand how to properly strengthen their knee and often wait too long to treat their injury. This combined with inconvenient, painful, useless or expensive treatment options may lead to situations in which those with injured knees view invasive surgery as their only option.
Knee strengthening methods require proper performance of the knee extension or leg extension exercise from an eccentric or stretched position to a concentric or contracted position of the muscles surrounding the knee, mainly the vastus medialis muscle. The main touchstone by which any strengthening program must be judged and which is universally accepted is specificity, overload, progression and regularity (SOPR).
The resistance must be specifically applied by selecting the proper movement. In the case of knee strengthening, it is the leg extension exercise targeting the vastus medialis and surrounding muscles. Overload stimulus must be applied in order to get a training effect or strengthening of the muscles and surrounding knee structures over time. This time may range from six weeks to three months, with results being achieved sooner if the trainee is diligent in performing their exercise. Overload is accomplished by slow but steady continual application of resistance each time the knee extension exercise is performed on a regular basis. Resistance should be easily controlled in the smallest increment possible by the user in order to gently but surely micro-load the muscles and surrounding knee structures over time. This micro-loading technique is highly respected and used to guarantee the quickest desired training effect without injury, as well as to motivate and safely train athletes.
Existing products range from leg extension machines to simple elastic tubing or ankle weights with vague instructions. Leg extension tables are large and expensive and, aside from the most costly commercial units, lack the gentle yet effective variable resistance and proper bio-mechanics. Thus, devices and techniques are needed that secure variable resistance in such a way as to make the knee-extension exercise bio-mechanically correct. It is also desirable to have a device with a resistance that is adjustable by the user at all times, and that is inexpensive and convenient enough that all those in need of help may benefit.